Growth of herpes simplex virus types 1 and 2 in tissues of fertile hens' eggs in ovo and in vitro.

The growth characteristics of herpes simplex virus Types 1 and 2 were examined on the chorioallantoic membrane of the fertile hen's egg and in cell cultures derived from egg and embryo tissues. After chorioallantoic membrane inoculation, the yield of infectious Type 1 virus was highest at 2 days and declined rapidly thereafter. With the Type 2 virus replication continued longer, titres were higher, and these declined more slowly over the 7-day incubation period. In cell cultures derived from embryo tissues, both virus types multiplied well, but Type 1 gave consistently higher titres of infectious virus. Type 2 virus produced higher titres in chorioallantoic membrane-derived cell cultures than did Type 1, reflecting the findings in ovo. Temperature-marker tests in eggs showed that fresh isolates of Type 1 virus grew less readily at elevated temperatures than those of Type 2 or laboratory-adapted Type 1 strains. There was no difference in the capacity of laboratory strains of either type to grow in eggs at these temperatures.